1. Technical Field:
This invention relates to pilot operated control valves for air, liquid and inert gas control.
2. Description of the Prior Art:
Control valves generally used in bleeding condensate from compressed air lines have comprised simple manually operated valves wherein a valve element is mechanically movable from a closed position on a valve seat in the valve to an open position and vice versa. Similar valves have been used in controlling lubricant supply lines to various devices and some have used mechanical and/or electrical devices for actuating the valves.
Control valves utilizing pressure of the controlled liquid are illustrated in my U.S. Pat. Nos. 4,733,696 and 4,733,697. In these disclosures, the valves comprise parts of replaceable cartridges which are used in manifolds positioned adjacent rolling mill stands that supply coolant to the rolls in desirable spray patterns. The coolant, such as kerosene used as used in the aluminum industry, is supplied to the spray nozzles through the cartridge valves from the coolant supply in the manifold in which the cartridge valves are located.
The pilot operated control valve of the present invention is formed with a main poppet valve element normally closing a passageway communicating with a compressed air line and a drain line so that upon automatic periodic operation, condensate in the main air line may be removed therefrom and directed to a drain or other point of disposal. Other passageways in the pilot operated control valve communicate with a solenoid operated valve through which the pressure of the compressed air line is directed to the main poppet valve element wherein a pressure differential holds the main poppet valve element in closed position.
This invention eliminates the problems that have heretofore existed in connection with condensate drain valves in communication with compressed air lines and at the same time permits the ready adaptation of the valve for operation by a separate air source such as desirable when for example the valve is used to control periodic lubrication at desired points on a machine.